Communication systems are increasingly being required to provide a wide range of services, including different forms of information communicated and different communication characteristics. Information forms include voice, data, video, telemetry, and the like. Communication characteristics include quality, complexity, latency, reliability, cost, availability, portability, and the like. Infrastructure such as telecommunication systems, the Internet, and cable systems exist to provide long-haul routing and information content sourcing. However, difficulty remains in delivering this information to customers. This is particularly the case if the customer is located in a rural location, is communicating through portable equipment, or is mobile.
Traditionally, communication service providers have relied on copper wire or coaxial cable to connect distribution sites and subscriber premises. However, increases in the number of users, number and type of communication devices per user, and the information rate per device has strained the ability for traditional communication systems to provide the necessary bandwidth and flexibility. Various technologies including digital subscriber line (DSL) and video modems offer broadband access to the subscriber over existing copper or coaxial loop technologies. Fiber-to-the-home offers broadband access through additional wireline connections. While each technology has broadband delivery properties, each is subject to physical and signaling limitations that restrict availability in certain locations and for certain applications. For example, VDSL is limited to within approximately one kilometer of a connecting central office. Further, each central office usually cannot support high-speed access for every customer within the central office coverage area. Similarly, service provided by two-way cable modems is limited to the installation of coax, hybrid fiber coax and fiber-based systems by the cable provider as well as support capabilities of the supporting central office. Currently, many premises do not have access to high-speed wireline voice, data, and video services due, in part, to the expense and difficulty in constructing or expanding central offices.
Wireless systems, such as PCS and cellular systems, offer an alternative to wireline services. Typically, wireless systems include a centralized mobile switching center (MSC) responsible for routing calls, tracking user locations, billing information, and connectivity with other communication systems. The MSC is connected to base station controllers (BSCs), each of which supports one or more base transceiver stations (BTSs). Each BTS supports one or more cells based on the number and configuration of antennas supported by the BTS. Customers communicate with the wireless system through radio telephones when the telephone is within the coverage range of a cell. When a call is placed, a circuit-switched connection is established from the telephone, through the BTS and BSC, to the MSC. The MSC determines the destination and, if the destination is to another telephone within the wireless system, establishes a circuit-switched connection to the destination telephone. If the destination is outside of the wireless system, the MSC routes the call to a service provider for the outside destination.
Cellular and PCS wireless systems have traditionally focused on voice. However, recent introduction of digital radio in both the 800 MHZ and 1.9 GHz permits low-speed data services, such as text messaging and one-way paging, to be implemented. Also, wireless modems implementing wireless application protocols may be incorporated into hand-held devices such as lap top personal computers and personal digital assistants (PDAs). Such devices may offer access to the Internet at rates up to 19.2 kilobits per second.
Several problems have developed with traditional wireless systems. First, because all calls are processed by the central MSC, it can become a bottleneck limiting the number of users supported. Second, if the MSC fails, the system becomes inoperative. Third, the BSC and BTS architecture is fairly rigid, requiring manual reconfiguration in the MSC when components are added or deleted. Fourth, circuit-switched channel connections establish an upper bandwidth, limiting communication rates. Fifth, bandwidth is wasted if the communication rate does not reach the maximum established by the communication channel. Sixth, high-speed data and video applications are impractical on wireless telecommunication systems designed primarily for voice.
An alternative wireless communication system is the multi-channel multipoint distribution system (MMDS). In MMDS, an antenna broadcasts high-bandwidth content to local receiving antennas. In the case of Internet access, the return path is typically through slow telephone lines. MMDS, like wireline cable systems, is asymmetrical, making it best suited for distribution of one-way entertainment signals such as television. MMDS also typically operates at a higher carrier frequency than PCS systems, requiring receiving antennas to be positioned in line-of-site with the transmitting antenna. MMDS is typically deployed in a single cell broadcast architecture. Other wireless communication systems, such as local multipoint distribution system (LMDS) may be deployed in a cellular fashion. However, because these systems typically operate at a high carrier frequency, receiving antennas must be positioned in line-of-sight with the transmitting antenna.
What is needed is a communication system that provides voice, data, and video signals at rates appropriate for each user. The system should make efficient use of bandwidth, allocating only the bandwidth necessary for a particular communication. The system should be flexible, permitting automatic addition and deletion of network components. The system should have distributed routing and service provisioning to prevent bottlenecks, permit scaling, and increase reliability and robustness. The system should support wireless subscriber units, accommodating a wide variety of fixed, portable, and mobile user communication devices. The system should support high-speed symmetric communication for applications such as video conferencing, real-time distributed document sharing, and the like. The system should also easily and rapidly adapt to mobile and portable users that change location throughout the communication system.